This invention relates to an automatic ice making machine, more particularly to an automatic ice making machine equipped with a protection unit which can effectively prevent compressor burning and waste of power during ice making operation.
Various types of automatic ice making machines for continually making various shapes of ice cakes including cube and plate in large quantities are utilized suitably depending on the applications. For example, popular ice making machines include:
(1) so-called closed cell system ice making machines having a multiplicity of freezing cells opening downward formed in a freezing chamber, in which the freezing cells can separably be closed with a water tray, and a water for freezing is injected into the freezing cells through the water tray to form ice cubes gradually therein; PA1 (2) so-called open cell system ice making machines having a multiplicity of freezing cells opening downward, in which a water to be frozen is directly injected into the freezing cells in the absence of the water tray to form ice cubes in the freezing cells; and PA1 (3) flow-down system ice making machines having a tilted freezing plate, in which a water to be frozen is supplied to flow on the upper or lower surface of the freezing plate to form an ice plate on the corresponding surface. PA1 (1) a temperature detector comprising a temperature element such as thermistor disposed, for example, on the side wall of the freezing chamber is allowed to monitor the sudden temperature rise which is observed when the ice cakes formed in the freezing chamber are released or drop, and completion of the ice releasing operation can be detected upon detection of temperature rise to a predetermined level by the temperature detector; or PA1 (2) a detection member comprising a rod and the like disposed on the way that the ice cakes released from the freezing chamber slide down into an ice reservoir and the like so that the ice cakes may hit the detection member to shift its position, and a microswitch is allowed to be depressed and actuated by the shifting of the detection member, whereby completion of the ice making operation can be detected. PA1 (1) if the ice releasing operation is continued, the temperature of the freezing chamber having released the ice cakes continues to rise rapidly to make the cooling medium to be sucked into the compressor through a suction pipe from the evaporator on the freezing chamber remain as a heated gaseous phase, so that not only the internal temperature of the compressor in the freezing system rises rapidly but also the temperature of the gaseous cooling medium discharged from the compressor further rises. Accordingly, the compressor performs an overload operation due to the rise in the internal pressure within the freezing system circuit and the rise in the internal temperature of the compressor, to increase the motor current and overheat the compressor case; and PA1 (2) an overload protection unit generally disposed for the compressor is designed to be actuated when the temperature of the compressor case is elevated beyond the predetermined level to shut off the power supply to the compressor and stop the operation thereof. However, if the compressor is stopped, the pressure of the cooling medium within the freezing system circuit gradually drops and the temperature of the compressor itself is gradually lowered due to natural heat dissipation, so that the overload protection unit of the compressor is automatically reset to resume energization of the compressor and thus the overload operation. Then, the overload protection unit is actuated again to repeat the cycle of stopping and overload operation.
These automatic ice making machines generally have an ice making mechanism in the upper part of the machine body and a freezing system for cooling said ice making mechanism at the lower part thereof, said freezing system comprising a compressor, a condenser, a capillary tube, an evaporator, etc.
The evaporator connected to this freezing system is disposed at the ice making section in the ice making mechanism to cool the ice making section; whereas a water to be frozen is circulably fed to the ice making section being cooled to form ice cakes, and upon detection of the growth of the ice cakes to a predetermined size by an ice formation detector which detects completion of ice formation, feeding of the water to be frozen is stopped. Subsequently, by the selective operation of a valve, a heated gaseous cooling medium from the compressor is adapted to be fed through a bypass tube to the evaporator to heat the ice making section and allow the ice cakes formed therein to drop by their own weight, whereby the ice cakes thus released are collected and accumulated in a stocker disposed below the ice making section. Incidentally, a fin and tube type condenser is generally used as the condenser of the freezing system which is forced to be cooled by a cooling fan.
As described above, a heated gaseous cooling medium is directly fed to the evaporator during the ice releasing operation, wherein the condensing power of the condenser is generally lowered for the purpose of preventing the liquid phase cooling medium to stay in the condenser and also increasing the internal pressure within the freezing system circuit. Further, the heating of the evaporator is accelerated by increasing the amount of the circulating gaseous cooling medium.
As a way of lowering the condensing power of the condenser, it is generally performed to stop operation of the air cooling fan motor therefor in an air cooling system condenser, whereas to stop supply of cooling water in a water cooling system condenser.
On the other hand, in order to detect completion of the ice releasing operation, the following methods are generally employed:
In the conventional automatic ice making machine described above, when the ice formation detector is rendered out of order or rendered incapable of detecting completion of ice formation during the ice releasing operation for some reasons, the ice releasing operation is continued even after the ice cakes are actually released completely to cause the following problems:
Namely, when the ice releasing operation is continued as the result of failure in detecting completion of ice releasing operation, the compressor repeats the overload operation and stopping alternatively unless the user recognizes it to take some measures. This overload operation causes not only waste of power but also deterioration of lubrication oil in the rotary section of the compressor. If the lubrication oil is thus deteriorated, smooth movement of the sliding section is inhibited to accelerate abrasion, leading to burning of the compressor itself to cause locked state or burning of the motor. Further, problems occur that the ice cakes in the ice reservoir melt due to the overheating of the freezing chamber and that the members disposed adjacent to the freezing system undergo deformation or burning. Moreover, the continued ice releasing operation causes the water to be frozen to be kept supplied from the external water supply system to the water feeding system to waste enormous amount of the water.
On the other hand, if the solenoid valve which performs selective operation of opening/closing the bypass tube for some reasons including burning, the following problems arise: if the solenoid valve is incapable of performing the selective operation to open the bypass tube even after the ice releasing operation is started, the heated gaseous cooling medium cannot flow into the evaporator through the bypass tube but only through the capillary tube. Accordingly, the cooling medium is evaporated at a low temperature in the evaporator like in the ice making operation to cool the freezing chamber, so that the ice cakes cannot be released from the freezing chamber with the ice releasing operation being continued to waste power and water.
This invention has been proposed in view of the problems inherent in the conventional automatic ice making machines as described above and for the purpose of overcoming them successfully, and is directed to provide an automatic ice making machine equipped with an inexpensive protection unit which can prevent compressor burning and waste of power and water.